boards/stm32f103-minimum: fix unaligned pointer to .data section in ld.script

[fbraghiroli]

This patch fix _eronly value which is used during boot process to initialize .data section to sram.

Since .data section is 4 byte aligned in flash, also _eronly must follow this alignment to stay coherent with the start address of .data.

If one of the sections preceeding .data has a size which is not 4 byte aligned, the _eronly value does not match with .data physical address resulting in wrong copy of data section to sram and thus an almost immediate hardfault.

Summary

This is a bugfix in linkerscript of stm32f103-minimum board.
_eronly is wrongly set and this caused data section to be copied to sram with additional garbage padding.
This happens when, for example, the .text section size is not a multiple of 4bytes (.text preceeds .data in elf map)
Similar bug has been fixed in e7ed720

Impact

Currently this has no impact.
There might be other boards with the same exact problem and this seems to have originated in commit 2925c28 , when ALIGN(4) has been added to some sections.

Testing

Test setup:

• arm-none-eabi-gcc (15:13.2.rel1-2) 13.2.1 20231009
• Dev system: ubuntu 22.04 64 bit
• nuttx master: e2a9c84
• Board: stm32f103 "blupill"
• NuttX configuration: tools/configure.sh -l stm32f103-minimum:nsh

Code to trigger the bug:

diff --git a/boards/arm/stm32/stm32f103-minimum/src/stm32_bringup.c b/boards/arm/stm32/stm32f103-minimum/src/stm32_bringup.c
index 7849cb9e51..3a2fc17b8b 100644
--- a/boards/arm/stm32/stm32f103-minimum/src/stm32_bringup.c
+++ b/boards/arm/stm32/stm32f103-minimum/src/stm32_bringup.c
@@ -240,6 +240,8 @@ static int g_sensor_devno;
  *
  ****************************************************************************/
 
+const char msg[] = "as";
+
 int stm32_bringup(void)
 {
 #ifdef CONFIG_ONESHOT
@@ -578,5 +580,7 @@ int stm32_bringup(void)
   usbdev_adb_initialize();
 #endif
 
+  syslog(LOG_ERR, "msg: %s\n", msg);
+
   return ret;
 }

Please note that in the code snippet, msg[] might be increased or decreased in order to have an unaligned .text size

Result (BUG)

uart:
�ABC

gdb:
Thread #1 (Suspended : Signal : SIGINT:Interrupt)
stack_dump() at assert.c:182 0x800111c
dump_stackinfo() at assert.c:232 0x8001392
dump_stacks() at assert.c:329 0x8001392
dump_running_task() at assert.c:653 0x8001392
dump_assert_info() at assert.c:707 0x8001392
_assert() at assert.c:892 0x8001392
__assert() at lib_assert.c:38 0x8003fc6
irq_unexpected_isr() at irq_unexpectedisr.c:56 0x80010c4
arm_doirq() at arm_doirq.c:90 0x8000ba8
exception_common() at arm_exception.S:214 0x80008e8

$ arm-none-eabi-readelf -a nuttx
...
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
LOAD 0x001000 0x08000000 0x08000000 0x0c3e7 0x0c3e7 R E 0x1000
LOAD 0x00e000 0x20000000 0x0800c3e8 0x001a0 0x00f28 RW 0x1000
...
1781: 0800c3e7 0 NOTYPE GLOBAL DEFAULT ABS _eronly

Note that _eronly is wrongly set to 0x0800c3e7 instead of 0x0800c3e8

Result (BUGFIX)

uart:
ABCDF
msg: as

NuttShell (NSH) NuttX-12.6.0-RC1
nsh>

arm-none-eabi-readelf -a nuttx

Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
LOAD 0x001000 0x08000000 0x08000000 0x0c3e7 0x0c3e7 R E 0x1000
LOAD 0x00e000 0x20000000 0x0800c3e8 0x001a0 0x00f28 RW 0x1000

1781: 0800c3e8 0 NOTYPE GLOBAL DEFAULT ABS _eronly